The Simpsons' Cupcake Mistake

I have a habit of spotting continuation mistakes in TV programs, especially ones that are so blatant and sometimes it happens in cartoons/animation, but those aren’t so obvious… unless you’re the increasingly unfunny, hipstertastic Simpsons.
Milhouse throws a couple of cupcakes at Lisa’s bedroom window, but look at the pane they landed on, now look at the window she’s sliding open, surely it will knock those cupcakes off..?!
Oh, apparently not, they must be magical cupcakes since the window passed right through them.
Even Lisa seems a bit bamboozled at how the cupcakes managed to stay stuck to the window.